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Dexmethylphenidate
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| Systematic (IUPAC) name | |
| (R,R)-(+)-Methyl 2-phenyl-2-(2-piperidyl)acetate | |
| Identifiers | |
| CAS number | |
| ATC code | N06 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C14H19NO2 |
| Mol. mass | 233.31 g/mol |
| Pharmacokinetic data | |
| Bioavailability | 11 – 52% |
| Protein binding | 30% |
| Metabolism | Liver |
| Half life | 2 – 4 hours |
| Excretion | Urine |
| Therapeutic considerations | |
| Pregnancy cat. |
C |
| Legal status |
Controlled (S8)(AU) Schedule III(CA) Class B(UK) Schedule II(US) |
| Routes | Oral |
Dexmethylphenidate (sold commercially by Novartis as Focalin, also available generically in the US exclusively from Teva) is a pharmaceutical drug used to treat Attention Deficit Hyperactivity Disorder. It is a psychostimulant dopamine reuptake inhibitor that affects the central nervous system. Dexmethylphenidate has a 4-6 hour duration of effect (a long-acting formulation, Focalin XR, which spans 12 hours is also available), and has been demonstrated to be as, if not more effective than methylphenidate at reducing the symptoms of childhood ADHD,1 as well as ADHD in adults.2
Dexmethylphenidate has a similar side-effect profile to racemic methylphenidate (Ritalin)3 and can be administered without regard to food intake.4 Recently, it has become available in extended-release form (Focalin XR) and has been shown to be as effective as d,l-methylphenidate XR (Concerta, Ritalin LA), with flexible dosing and good tolerability.56
Contents |
Mode of action
Methylphenidate is a well-known inhibitor of catecholamine reuptake--it increases trans-synaptic concentrations of the neurotransmitters dopamine and noradrenaline by inhibiting the action of the respective neurotransmitter transporter proteins (DAT and NET) responsible for moving these transmitters back into the presynaptic neuron. Chemically, there are four possible stereoisomers of methylphenidate, however, only the stereoisomers possessing the threo configuration are used clinically. As usually synthesized, threo-methylphenidate (Ritalin) is a racemate, consisting of two molecules with identical chemical structures but different chirality. Dexmethylphenidate consists of the isomer that is far more effective in binding to the neuronal DAT,78 with the inactive enantiomer (l-threo-methylphenidate) removed. Because of this, an individual's therapeutic dose of dexmethylphenidate will generally be half their therapeutic dose of methylphenidate.
The same concerns that apply to other stimulant drugs should be considered: Reports of sudden cardiac death in children caused Canada to stop marketing Adderall XR (another stimulant used to treat ADHD) for a period in 2005 (however, Adderall XR was returned to the market in that same year after it was demonstrated that cardiac risk is low in patients free of congenital heart defects). Heart problems have been reported, predominantly in young people taking ADHD stimulants, though the FDA has not concluded that psychostimulants increase risk of cardiac problems for a person without a heart condition. Suicidal thinking has been reported in young people who are taking antidepressants at the same time they are taking an ADHD stimulant and many antidepressants carry a "black box" FDA warning label concerning a possible increase in suicidal thoughts in patients under 18 years of age.
Therapeutic use
Dexmethylphenidate is used as a treatment for ADHD, ideally in conjunction with psychological, educational, behavioral or other forms of treatment. It is proposed that stimulants help ameliorate the symptoms of ADHD by making it easier for the user to concentrate, avoid distraction, and control behavior. Dexmethylphenidate may also improve listening skills and organization of tasks, and may help prevent tic disorders. Because it is a psychostimulant, dexmethylphenidate may also help with narcolepsy and in certain cases of major depression.
Typical daily doses of dexmethylphenidate are around 10-20mg for children and 20-40mg for adults. As with all psychostimulant compounds, certain individuals may respond to a small dose and certain individuals may require a larger than average dose, hence, dosing is usually initiated at a typical range and then titrated to suit the patient. Typically an individual's active dose of dexmethylphenidate will be half the dose of methylphenidate, as the l-enantiomer of methylphenidate contributes little to the human pharmacology of the drug.9
There is a possibility of withdrawal symptoms if dexmethylphenidate use is discontinued suddenly. As with other stimulants, withdrawal symptoms may include emotional or behavioral depression. Tapering off is recommended, under the supervision of a doctor. Addiction, which involves compulsive or harmful drug-seeking behavior, is rare but not impossible.10
Negative effects
Focalin
Trouble sleeping, nausea, stomach pain, headache, nervousness, loss of appetite, or weight loss are common side effects.
Rare but much more serious side effects: Uncontrolled muscle movements (e.g., stiffness, twitching, shaking), high fever, outbursts of words/sounds, swelling of the ankles/feet, blurred vision, mental/mood/behavior changes (e.g., agitation, aggression, mood swings, depression, hallucinations, abnormal thoughts/behavior), extreme tiredness, and severe sweating, easy bleeding/bruising, shortness of breath, fainting, chest/jaw/left arm pain, sudden vision changes, signs of infection (fever, persistent sore throat), fast/irregular/pounding heartbeat, weakness, seizures, confusion, slurred speech, and severe headaches and in some rare cases, death.
Also, there is a potential for a severe allergic reaction, but it is extremely rare. Trouble breathing, itching, a rash, swelling, or severe dizziness are all signs/symptoms of this allergic reaction.
FocalinXR
FocalinXR has all the same negative effects that Focalin has; the XR also includes heartburn, dizziness, dry mouth as a more common negative effect. 11
Usage
The FocalinXR capsules are sometimes prescribed over other extended release stimulants because the capsules can be opened and their contents mixed with applesauce or pudding to help children who cannot, or will not, swallow large capsules. This is possible due to the SODAS (Spheroidal Oral Drug Absorption System) delivery system, also used in Ritalin LA. Focalin XR come in five, ten, fifteen, and twenty milligram capsules. To determine appropriate dosage doctors first prescribe one to four 5mg capsules. An appropriate treatment plan is then based on the patient's reaction to the initial dose. 12
See also
- Amphetamine-- Adderall
- Atomoxetine-- Strattera
- Dextroamphetamine-- Dexedrine
- Methylphenidate-- Concerta, Ritalin
- Lisdexamfetamine-- Vyvanse
- Methamphetamine-- Desoxyn
References
- ^ Arnold, L.E., et al. (2004). "A double-blind, placebo-controlled withdrawal trial of dexmethylphenidate hydrochloride in children with attention deficit hyperactivity disorder". J Child Adolesc Psychopharmacol. 2004 Winter;14(4):542-54.
- ^ Spencer TJ, Adler LA, McGough JJ, et al. (2007). Efficacy and safety of dexmethylphenidate extended-release capsules in adults with attention-deficit/hyperactivity disorder. Biol Psychiatry. 61(12): 1380-7.
- ^ Keating, G.M. & Figgitt, D.P. (2002). "Dexmethylphenidate". Drugs. 2002;62(13):1899-904; discussion 1905-8.
- ^ Teo, S.K., et al. (2004). "A Single-Dose, Two-Way Crossover, Bioequivalence Study of Dexmethylphenidate HCl with and without Food in Healthy Subjects". J Clin Pharmacol. 2004 Feb;44(2):173-8.
- ^ McGough J.J., Pataki C.S., Suddath R. (2005). "Dexmethylphenidate extended-release capsules for attention deficit hyperactivity disorder". Expert Rev Neurother. 2005 Jul;5(4):437-41.
- ^ Silva, R., et al. (2004). "Open-Label Study of Dexmethylphenidate Hydrochloride in Children and Adolescents with Attention Deficit Hyperactivity Disorder". J Child Adolesc Psychopharmacol. 2004 Winter;14(4):555-63.
- ^ Ding YS, Fowler JS, Volkow ND, et al. (1997). Chiral drugs: comparison of the pharmacokinetics of [11C]d-threo and l-threo-methylphenidate in the human and baboon brain. Psychopharmacology. 131: 71-78.
- ^ Davids E, Zhang K, Tarazi FI, et al. (2002). Stereoselective effects of methylphenidate on motor hyperactivity in juvenile rats induced by neonatal 6-hydroxydopamine lesioning. Psychopharmacology. 160: 92-98
- ^ Quinn, D. (2008). Does Chirality Matter?: Pharmacodynamics of Enantiomers of Methylphenidate in Patients With Attention-Deficit/Hyperactivity Disorder. Journal of Clinical Psychopharmacology. 28(3) (Suppl. 2): S62-S66.
- ^ "Oral Uses".
- ^ "Drug Treatments-Focalin".
- ^ "Focalin XR for ADHD".
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- This page was last modified on 13 November 2008, at 05:15.
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